hook and eye

a two-piece clothes fastener, usually of metal, consisting of a hook that catches onto a loop or bar.

2.

a three-piece latching device consisting of a hook attached to a screw eye or an eyebolt and a separate screw eye or eyebolt that the hook engages as it bridges a gap, as one between a door and a jamb or a gate and a gatepost.

3.

Also called eyehook. the two-piece portion of such a device consisting of a hook and a screw eye.